The major objective of this research project is to continue an investigation of the neural organization of the supranuclear substrates of the primate oculomotor system. The proposed experiments utilize the technique of recording the activity of single neurons in the brain stem and cerebellum of fully alert, behaving monkeys coupled with a sensitive, drift-free magnetic field method of measuring eye position. This technique will be applied in the experiments outlined below in order to provide some of the further detailed knowledge required to establish a solidly based picture of the immediate pre-motoneuronal organization: (1) Neurons in the vestibular nucleus and in the floccular lobe of the cerebellum which show a discharge rate that can be related to eye movements will be studied during a wide frequency range of rotatory and optokinetic stimulation and for various combinations of these two inputs. (2) The order of each vestibular neuron with respect to primary vestibular input will be tested with a stimulating electrode chronically implanted in the VIII th nerve. (3) The visual field properties and eye-muscle stretch receptor input to eye movement related floccular cells will be investigated. (4) The behavior of both pontine reticular and vestibular nucleus neurons will be studied during vergence movements. Clarification of the neural mechanisms underlying monocular accommodative vergence movements will be sought. (5) The integration of head into coordinated eye-head movements at the level of the pontine reticular formation will be investigated in order to clarify the role of thos reticular unit types more randomly related to eye movement control.